US 7729841 B2
In a method and a device for predicting movement trajectories of a vehicle to prevent or reduce the consequences of an imminent collision, in which for predicting the movement trajectories, only those trajectories are considered for which, because of a combination of steering intervention and braking intervention, the forces occurring at the wheels of the vehicle are within the range corresponding to the maximum force transferable from the wheel to the road. Particularly for systems which provide an automatic braking and/or steering intervention for avoiding a collision or reducing the severity of a crash with another object, an automatic braking and/or steering intervention is carried out as a function of the pre-calculated movement trajectories.
1. A method for predicting movement trajectories of a vehicle for one of preventing a collision and reducing crash severity, comprising:
predicting all movement trajectories of the vehicle for which forces occurring at wheels of the vehicle are, at each instance of each of the trajectories, a maximum force capable of being transferred from the wheels to a road without the wheels losing adhesion to the road, the maximum force capable of being transferred from the wheels to the road being substantially equal to μmax*Fn, μmax being a coefficient of friction between a roadway and a tire of the wheels of the vehicle, Fn being a vertical force applied by the vehicle to the roadway, the movement trajectories having a combination of steering actuation and brake actuation;
determining μmax in accordance with signals from at least one of an anti-lock device and an electronic stability program;
detecting an object by a surroundings sensor system, the surroundings sensor system including at least one of a radar sensor, a lidar sensor and a video sensor; and
wherein the determining μmax includes evaluating additional signals from a rain sensor.
2. The method according to
one of avoiding a collision of the vehicle with the object detected by the surroundings sensor system and reducing a severity of an unavoidable crash in accordance with the predicted movement trajectories in at least one of automatic control of deceleration devices and automatic control of vehicle steering devices.
3. A device for predicting movement trajectories of objects, comprising:
at least one surroundings sensor system configured to supply signals;
a prediction device configured to pre-calculate all movement trajectories of a vehicle, having a combination of steering actuation and brake actuation, for which forces occurring at wheels of the vehicle are, at each instance of each of the trajectories, a maximum force capable of being transferred from the wheels to a road without the wheels losing adhesion to the road, the maximum force capable of being transferred from the wheels to the road being substantially equal to μmax*Fn, μmax being a coefficient of friction between a roadway and a tire of the wheels of the vehicle, Fn being a vertical force applied by the vehicle to the roadway; and
a rain sensor;
wherein μmax is determined in accordance with signals from at least one of an anti-lock device and an electronic stability program;
wherein the surroundings sensor system detects an object, the at least one surroundings sensor system including at least one of a radar sensor, a lidar sensor and a video sensor; and
wherein additional signals from the rain sensor are evaluated for determining μmax.
4. The device according to
5. The device according to
6. The device according to
an arrangement configured to calculate movement trajectories for the vehicle and the object detected by the surroundings sensor system; and
an output device configured to automatically actuate at least one of vehicle deceleration devices and vehicle steering devices.
This application is a U.S. national phase patent application of PCT/DE02/02538, which was filed Jul. 11, 2002, and claims priority to and the benefit thereof and of German patent application no. 10133029.4, which was filed in Germany on Jul. 11, 2001, the disclosures of which are incorporated herein by reference in their entirety.
The present invention relates to a method and a device for predicting movement trajectories of a vehicle to prevent a collision or reduce the severity of the crash, in which for predicting the movement trajectories, only those trajectories are considered for which, because of a combination of steering intervention and braking intervention, the forces occurring at the wheels of the vehicle are, e.g., as great as the force transferable at a maximum from the wheel to the road. Particularly for systems which provide an automatic braking and/or steering intervention for avoiding a collision with another vehicle, an automatic braking and/or steering intervention is carried out as a function of the pre-calculated movement trajectories.
In recent years, adaptive cruise controllers have increasingly come on the market which expand the conventional control of a vehicle-speed controller to the effect that the distance and relative velocity of the preceding vehicle are detected by a radar or lidar system, and this data is utilized for the speed control and/or distance control of one's own vehicle.
Such a system is described in the paper “Adaptive Cruise Control System—Aspects and Development Trends” by Winner, Witte et al., SAE paper 96 10 10, International Congress and Exposition, Detroit, Feb. 26-29, 1996.
In the publication “A Trajectory-Based Approach for the Lateral Control of Vehicle Following Systems” by Gehrig and Stein, presented at the IEEE International Conference on Intelligent Vehicles, 1998, an algorithm is described, which, from the measured data of a radar or lidar sensor, creates a movement trajectory of the preceding vehicle, and controls one's own vehicle according to it. Particularly for movements in which both vehicles are driving into or out of a curve, special demands are made on such a trajectory algorithm. An algorithm of this type for determining movement trajectories is presented by way of example in the aforesaid document.
In the book “Fahrwerktechnik: Fahrverhalten” by Zomotor, from Vogel Book Publishing, Würzburg, first edition 1987, in chapter 2, “Forces on the Vehicle”, the theoretical fundamentals are explained which are necessary for understanding the transfer of force between tire and roadway.
When pre-calculating all possible movement trajectories of a preceding vehicle or of one's own vehicle, great demand for computing power may be made on the prediction system for pre-calculating the further movement. This may be because a great number of possible movements of the vehicle may be taken into account. Particularly in dangerous situations, in which a strong deceleration or a sharp steering movement may be expected, this large number of possible movements may increase even further. Since in this case, a real-time processing of the movement trajectories may be desired, it may be necessary to use a powerful computer system.
In this context, it may be provided in calculating the movement trajectories, which in the case of an imminent collision may result from steering operations, braking operations or combined steering and braking operations, to be able to calculate them in advance. To minimize the computing expenditure, it may be provided that only those trajectories be pre-calculated for which, because of a combination of steering intervention and braking intervention, the force occurring at the wheels of the vehicle is in the range of the maximum force transferable from the wheel to the road. It may be assumed that, in response to driving through one of these trajectories, the imminent collision with an object may be prevented, or, in the event that a collision may not be avoidable, it may at least be possible to reduce the severity of the crash. To be understood by crash severity is, in this case, the extent of damage from the collision, which may be dependent on the impact energy, but also, for example, on the constitution of the object. Thus, for example, given equal impact energy, the crash severity for a collision with a concrete wall may be greater than for a collision with a preceding vehicle.
This method for pre-calculating movement trajectories may be used on one's own vehicle that is equipped with a radar, lidar or video system, but also on other vehicles detected by the surroundings sensor system.
It may be provided that the surroundings sensor system is composed of a radar sensor, a lidar sensor, a video sensor, etc., or a combination thereof. If a vehicle is equipped with more than one surroundings sensor, it may be possible to ensure a more reliable and higher-resolution detection.
Moreover, it may be provided that the maximum force transferable from the wheel to the road may be corrected as a function of an instantaneous situation. In particular, this maximum transferable force may change due to wetness or snow on the roadway. To ascertain the instantaneous roadway coefficient of friction, which co-determines the maximum force transferable from the wheel to the road, the signals from an anti-lock device and/or an electronic stability program may be utilized. Moreover, it is also possible that signals from further surroundings sensors, such as a rain sensor or a poor-weather detection, may be utilized by the radar, lidar or video sensor system for determining the instantaneous wheel-slip value.
In addition, it may be provided that the predicted movement trajectories may be used for the automatic control of the deceleration devices and/or for the automatic control of the vehicle steering devices, in order to avoid an imminent collision with a preceding vehicle or object.
The method according to the present invention may be implemented in the form of a control element provided for a control unit of an adaptive distance and/or speed control of a motor vehicle. In this context, the control element has stored on it a program that may be executable on a computing element, e.g., on a microprocessor, an ASIC, etc., and may be suitable for carrying out the method of the present invention. Thus, in this case, the present invention may be realized by a program stored on the control element, so that this control element provided with the program may constitute an example embodiment of the present invention in the same manner as the method, for whose execution the program may be suitable. An electrical storage medium, e.g., a read-only memory, may be used as control element.
Further features, uses and aspects of the present invention are described in the following description of exemplary embodiments of the present invention which are illustrated in the drawings. In this context, all of the described or represented features, alone or in any combination, form the subject matter of the present invention, regardless of their combination, as well as regardless of their formulation and representation in the following description and drawings, respectively.
In the following description, exemplary embodiments of the present invention are explained with reference to the Drawings.
Another possibility for avoiding a collision in the traffic situation described may be a pure evasion maneuver. In this case, one may not carry out a braking intervention, but rather may provide as sharp a steering angle as possible. Such a procedure is represented by double-dotted movement trajectories 11 and 12. In this case, one may have a longitudinal force 3 equal to zero and a maximum transverse force 4 in the construction of Kamm circle 2. During this maneuver, it may easily happen that, due to too sharp a steering angle, the maximum possible lateral force may be exceeded and the vehicle may go into a spin. A combined braking and steering intervention, as is represented by triple-dotted movement trajectory 14, may be provided in the traffic situation illustrated. To clarify the combined braking and steering intervention, reference is made to
The pure steering maneuver as is illustrated in
The combined braking/steering maneuver according to triple-dotted movement trajectory 14 is illustrated in the y-x diagram of
The method of the present invention may calculate all possible movement trajectories which are between the two extreme trajectories illustrated, namely, on one hand, a pure full brake application without steering intervention 13, and on the other hand, a maximum possible steering movement without braking intervention 11 or 12. However, all the calculated trajectories may have in common that the forces affecting the wheels correspond, e.g., to the forces arranged on the Kamm circle.
In this context, a great number of possible movement trajectories may be possible. The trajectories which, within their course, have points at which the force resulting from the longitudinal and lateral components becomes considerably greater or considerably smaller than is permitted by the Kamm circle illustrated in
The frictional grip of the wheel on the roadway is variable due to changes in the weather conditions or the outside temperature. To take these changes of the coefficient of friction μmax into account, the radius of Kamm circle 2 is constantly updated. This is accomplished, for example, by taking into account the outside temperature, by taking into account the weather conditions, in that a signal from a rain sensor is supplied, and in that interventions of an anti-lock device or an electronic stability program are evaluated, and changes in the coefficient of friction are passed on to the automatic emergency braking system.